Author Topic: Injector rebuild (Read 8323 times)

dieselsmoke · « **on:** October 18, 2007, 05:21:02 pm »

I have been seaching through the posts but can't find much on injector rebuild. I bought new GTD nozzles to put into my injectors on my 1.9TD. Does anyone have a write up on the steps to rebuild them? Thanks

Vincent Waldon · « **Reply #1 on:** October 18, 2007, 06:16:55 pm »

One way is how I do 1.6 injectors:

http://vincewaldon.com/index.php?option=com_content&task=view&id=20&Itemid=28

I don't cover pop-testing (yet) but you need pretty specific gear for that... the general theory is if your injectors were close from a pop pressure perspective with the old nozzles they'll be be pretty close afterwards (assuming the springs and shims are all kept together as a set).

Also... my HOW-TO is specific to 1.6 injectors... haven't had my 1.9 injectors apart yet so no actual pictures.... coming soon.

Vince

dieselsmoke · « **Reply #2 on:** October 18, 2007, 06:39:47 pm »

that is an excellent write up. What is the torque that I am supposed to tighten them to once putting them back together? I know you said that you just reef on it but I am just curious about what the torque is supposed to be.

Vincent Waldon · « **Reply #3 on:** October 18, 2007, 06:50:54 pm »

Ah yes.... a work in progress !

The official torque is 70 Nm or 51 ft-lbs. I'll go back and add that in right now... thanks for catching it.

Vince

jtanguay · « **Reply #4 on:** October 18, 2007, 07:23:10 pm »

nice writeup! i'll try that on my tdi injectors

blkboostedtruck · « **Reply #5 on:** October 18, 2007, 08:08:31 pm »

Vince,
I got an old dealer mechanics repair manual! but in there it only states opening pressure like 120 to130 bar! what would be the pressure for GTD or injector's with merc. nozels? those #'s it gave must be for N/A injectors? or do i keep to the stamped pressures thats on the body? like 155 bar for TD injectors! or is it better to increase or decrease pressure for different applications?
thanks Duane

dieselsmoke · « **Reply #6 on:** October 18, 2007, 08:54:05 pm »

Excellent. I am going to give it a try next week and see how they turn out. I have to buy the sand paper yet. What is the purpose of the piece of glass? Can teh parts be cleaned in paint thinner or will that damage something

Vincent Waldon · « **Reply #7 on:** October 18, 2007, 08:57:47 pm »

Guess I better work on the pop-testing HOW-TO next.

What I do know is:

- stock breaking pressure for normally-aspirated VW diesels is 130-138 bar with a wear limit of 120 bar
- stock breaking pressure for 1.6l turbo diesel IDI engines is 155-163 bar with a wear limit of 140 bar
- stock breaking pressure for 1.9l turbo diesel IDI engines is 150-158 with a wear limit of 140 bar

I believe Mercedes run their TD engines at a slightly lower breaking pressure.... I'm guessing someone out there in dancing-man avatar land knows the numbers off by heart.

What's the *right* pressure. Ah, now you've opened the can of worms !!

What I can tell you is what I do. I don't have a good supply of shims. And, I think there's a balance between breaking pressure and pump losses. So, I'm fine losing a bit of breaking pressure when I calibrate my injectors and instead focus on getting them as close to each other as possible.

Let's say I have four injectors and they ring in at 155-150-160-155. I pick the lowest one (150) and leave it alone.... I then sand the remaining ones to match as close as I can to 150 bar.

This topic comes up often so search is your friend... and of course the word "right" can mean many things: power, fuel economy, smoke, noise, engine life. If I remember correctly the general concensis is that with today's diesel and an engine with good compression something around 140-145 is about the sweet spot for power and mileage... but that's just my recent memory.

Vincent Waldon · « **Reply #8 on:** October 18, 2007, 09:04:10 pm »

Quote from: "dieselsmoke"

Excellent. I am going to give it a try next week and see how they turn out. I have to buy the sand paper yet. What is the purpose of the piece of glass? Can teh parts be cleaned in paint thinner or will that damage something

Paint thinner would be a fine cleaning solvent... you could use kerosene, diesel, or JP2 from your Batmobile. Can't recommend anything with flammable fumes at room temperature... like gas for instance.

The glass is to give you a very very flat surface to sand on... and you want to go slow, keeping the surfaces as flat as possible on the sandpaper.

Dr. Bosch is of course rolling in his grave, since the right way to to this involves some kind of expensive micro grinder able to take off very precise and thin slices.

Again.... this is just how I do it BTW.... not everyone laps, some people use different grits than me, some only use two steps of sandpaper, etc etc etc. Your mileage may vary !!

Keep the suggestions coming people... I'll keep updating the HOW-TO.

Vince

Vincent Waldon · « **Reply #9 on:** October 18, 2007, 09:06:11 pm »

Quote from: "jtanguay"

nice writeup! i'll try that on my tdi injectors

IIRC the TDI nozzles and injector bodies are quite different... but for sure pull one apart and let us know what you find out.

Vince

windex · « **Reply #10 on:** October 19, 2007, 06:35:33 am »

Vince, I read through your pictorial, and the only question I have with my pending TD nozzle replacement (nozzles arrived from Smog today) is the selcetive shims -

I realize that "machining" the surfaces on the spacer and housing will lower spring tension and pop-pressure.

1) where does one obtain a selection of shims to increase the machined surface thickness?

2) would it not be suffient to take a micrometer to the sufaces befor milling, and add up the removed material in selecting a new shim (assuming the factory got it right in the first place)?

gnavs · « **Reply #11 on:** October 19, 2007, 07:19:02 am »

Amazing write up Vince.
I know they are 1.6 specific but there shouldn't too much different for the 1.9 right?

Vincent Waldon · « **Reply #12 on:** October 19, 2007, 08:07:56 am »

Quote from: "windex"

I realize that "machining" the surfaces on the spacer and housing will lower spring tension and pop-pressure.

1) where does one obtain a selection of shims to increase the machined surface thickness?

2) would it not be suffient to take a micrometer to the sufaces befor milling, and add up the removed material in selecting a new shim (assuming the factory got it right in the first place)?

I think it's a bit of a mixed bag.... machining the injector top would increase spring pressure and therefore breaking pressure a bit, and machined the spacer would decrease spring pressure a bit.

One of these days I'll measure a before and after and see if it's actually a big deal.

Like most things German-engineered, Bosch, and diesel-related it's an amazingly precise device... the spring pressure is very accurate and you can actually calculate how much to shave or add for each bar of pressure you need. Hence the shop with the big selection of shims... he/she can dial in injectors in one pass.

ETKA lists the part numbers of the wide selection of shims that *used* to be available (when I do my pop-testing HOW-TO I'll include 'em) but I don't know for sure if VW can still get them. I've heard Bosch shops can get them as well... dunno, cause the "sand them all down to the lowest one in the batch" has always worked for me... I know for sure I'm not interested in anything higher than 150-155 so I've never had to "shim up".

BTW... most people that I know sand the spring rather than the shim... the spring is a perhaps bit softer but definately much much easier to hold and lap. And, it's not a sealing surface so you can use coarser sandpaper.

Vince

Vincent Waldon · « **Reply #13 on:** October 19, 2007, 08:11:08 am »

Quote from: "gnavs"

Amazing write up Vince.
I know they are 1.6 specific but there shouldn't too much different for the 1.9 right?

I'm actually about to find out as I'm in the middle of a AAZ rebuild and will do the injectors while the head is off.

Externally they look the same, and I know people run 1.6 injectors on the AAZ head all the time, but the reading that I've done says that they use a "double spring" and "internal parts are no longer available... must be replaced as a unit". Double spring *might* mean a couple of different breaking pressures, or one break pressure and a different hold pressure... the next step in the evolutionary chain towards piezos that can deliver whatever, whenever, as fast as you want. Five small pulses and then one big pulse and a couple tiny ones at the end ?? No problem.

Anyways, something must be different with the AAZ internals ?!! I'll have one apart in about a week... or maybe someone here will beat me to it.

When I pull mine apart my camera will be at the ready !!

Vince

MikkiJayne · « **Reply #14 on:** October 19, 2007, 12:57:45 pm »

The TDI injector is a similar concept, but different in detail. The injector body is in a single piece, with only the nozzle coming off. It has two springs, and lots of shims and spacers. I can't post a decent pic right now because mine went 'spoing' when I took it apart, leaving a random pile of bits :roll:

When I take one of the others apart I'll pay a bit more attention to the order the bits come out in, and take some pics

Mikki x